4-Formylimidazoles and 5-formylimidazoles are useful as raw materials for the production of drugs, for example diuretics and antihypertensive agents, and are chemicals attracting attention in recent years.
As for the production of these formylimidazoles, only a very few references can be cited. The only production methods so far studied comprise using 2-alkyl-5-hydroxymethylimidazoles as starting materials and oxidizing these with a reagent containing a heavy metal, for example manganese dioxide, or with nitric acid. For the reagent oxidation method mentioned above, EP 0 514 198 A1 (under the heading "Intermediate 67") may be cited and, for the nitric acid oxidation method USP 4 107 308 for instance.
However, the method comprising oxidizing hydroxymethylimidazoles with a heavy metal reagent such as manganese dioxide is disadvantageous in that much labor is required for heavy metal handling or waste catalyst treatment and disposal. The method comprising oxidizing hydroxymethylimidazoles with nitric acid is very disadvantageous for commercial scale operation because of the low yield of the desired products and the generation of nitrogen oxides, among others.